# import sys

# for line in sys.stdin:
#     a = line.split()
#     print(int(a[0]) + int(a[1]))

#方法一：数学取模法
# a = int(input())
# b = a%10
# c = a%100//10
# d = a%1000//100
# e = a//1000
# print(b+c+d+e)

#方法二：字符串转换法
n = input()
print(sum(int(i) for i in n))